# Disaster strikes. How do I make swimming pool water drinkable? **URL:** \ **Category:** Factual Questions\ **Created:** [April 20, 2009, 7:32pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764 "2009-04-20T19:32:56Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [April 20, 2009, 11:53pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/21 "2009-04-20T23:53:29Z")
I’d say get one of those hiking water filters. Start by runing it through a Brita- type, then one of the hiking filters, then I think you’d be fine. Or a Brita then a Steri-pen. The problem with boiling is that you likely have less fuel than water, and fire is a danger. A water filter is an excellent survival tool. ---
**Author:** ![ArmenE](https://avatars.discourse-cdn.com/v4/letter/a/e9bcb4/32.png) [@ArmenE](https://boards.straightdope.com/u/ArmenE)\ **Post date:** [April 21, 2009, 12:28am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/22 "2009-04-21T00:28:07Z")
What’s with everyone wanting to distill the water? How will you know you’re not distilling out chlorine? In beermaking, if you accidentally get chlorine (from sanitization) into your wort (unfermented beer), you are generally instructed to re-boil the wort in order to boil off the chlorine. See C. Papazian The Joy of Home Brewing ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [April 21, 2009, 12:34am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/23 "2009-04-21T00:34:34Z")
> [@ArmenE](#): > > What’s with everyone wanting to distill the water? How will you know you’re not distilling out chlorine? Because it doesn’t matter. If you somehow wind up with chlorine in your distillate, you just let it sit a day or two and the problem will solve itself. In the meantime, the distillation has gotten rid of all bacteria, viruses, protists and most other potential nasties, such as fecal material, decay products or urine and other unwanted chemicals. If you need potable water, it’s THE simplest and most effective method of producing it from any water source. Even from a septic tank, if it came to that. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [April 21, 2009, 12:50am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/24 "2009-04-21T00:50:12Z")
First step is to stop shitting into your pool. With that taken care of, the water’s really not that bad. How do you think animals live? Or pre-fire humans? No, there wasn’t some antibacterial saliva or activated-charcoal throat-pouch that got lost to evolution. (Although you do need to start training your system a bit so that it won’t shit itself at the first whiff of a bacterium. But even if you get some diarrhea, that’s not quite the same as a serious illness.) > [@Lemur866](#): > > You don’t need to distill pool water to make it safe to drink. It’s already safe to drink. It’s not like it’s going to turn into a swamp in a day, and even if it has algae the algae isn’t toxic. What you have to worry about is animal feces and dead animals. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [April 21, 2009, 12:55am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/25 "2009-04-21T00:55:18Z")
> [@HorseloverFat](#): > > Distilling by using heat or even evaporation is how people in extreme circumstances survive. How would you go about distilling water with ambient evaporation? > [@](#): > > So even if the water goes bad why couldn’t you just hang a tarp over a section (all) of the pool? Raise the center of the tarp so it’s tent-shaped and manage the edges so that the water that condenses runs down to one of the corners and into a collection vessle? That sounded clever at first, but the sun’s just going to heat up the tarp way above ambient and nothing will condense on it. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [April 21, 2009, 12:55am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/26 "2009-04-21T00:55:53Z")
> [@Aji\_de\_Gallina](#): > > Bleach (the washing kind), at least in my house, doesn’t have enough concentration. You’d be pouring inordinate ammounts, even compared to liquid chlorine. Baloney. I don’t recall the exact amount, but for household bleach, its like DROPS of it per gallon of water to make nasty (biologically)water safe. So, you are talking tablespoons/small fractions of a cup for something in the hundred gallon range. Which means a gallon of house hold bleach will treat thousands of gallons of water off the top of my head. If you’ve got nasty water, some household bleach, and can stomach icky tasting water, your good to go as far as I know. ---
**Author:** ![brewha](https://avatars.discourse-cdn.com/v4/letter/b/91b2a8/32.png) [@brewha](https://boards.straightdope.com/u/brewha)\ **Post date:** [April 21, 2009, 1:05am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/27 "2009-04-21T01:05:56Z")
> [@Quartz](#): > > No. If there’s no wind, eventually your surface will heat up and water will no longer condense. What you need is a large flexible hose, some rope, and a blanket. And some wind. Coil the hose so the input is at the top and the output at the bottom. Hang the coiled hose from a tree or something. Soak the blanket (in water or urine) and drape it over the coil. The steam from your kettle or whatever goes in the top of the coil and the energy of first heating then evaporating the water in the wet blanket cools the steam giving you potable water out the other end of the coil. No? Just no? That’s funny. Allow me to respond in kind. Yes. I don’t recall specifying the size of the sheet. Do you really believe that you have to have wind to have heat transfer? Yes, wind increases it, but if the sheet were big enough, it would stay cool enough for condensation - even in still air. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [April 21, 2009, 1:33am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/28 "2009-04-21T01:33:56Z")
If there’s wind, the main way that wind will cool the condensation sheet is by… guess what… evaporating the water off it. I still don’t get how it works. To do it right, you’d have to attach a cooling loop using dirty water or an evaporation system using dirty water. But, I guess, a very large sheet and no wind (and no sun) may work. ---
**Author:** ![ivn1188](https://avatars.discourse-cdn.com/v4/letter/i/e480ec/32.png) [@ivn1188](https://boards.straightdope.com/u/ivn1188)\ **Post date:** [April 21, 2009, 5:50am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/29 "2009-04-21T05:50:21Z")
> [@brewha](#): > > ]but if the sheet were big enough, it would stay cool enough for condensation - even in still air. I’m confused too. Your idea is workable, but hideously inefficient. Your sheet of whatever would have to be very large and conductive, and you would lose a lot of vapor. An enclosed system is easier to make – a pot with a lid, a brick on top to keep it tight, and a hole to let steam out into a cooling tube of some sort. As for the solar still idea, it’s workable, but very slow and it doesn’t take advantage of the pool. Say the ambient temperature is 80 degrees. Disregarding solar effects (that would make the sheet hotter and the pool cooler), the sheet of whatever will be 80 degrees. The water will be 80 degrees. Water that evaporates from the pool would have no reason to condense, just like trees and benches and other things don’t condense water out of the air. Now, as the sun set, the temperature of the sheet would drop faster than that of the earth and water system (the pool), so you would get some condensation (which is why dew forms). The energy to power a still of any sort has to come from somewhere, because they work by converting the water to vapor and back, so you have to maintain a temperature difference between the ends of the still system, and the higher the difference the more water vapor you will capture. The day/night cycle is a way to get this for “free”, but it’s really really slow. A lens or solar collector would help, but it’s still going to be very slow – a pool has incredible thermal mass. I don’t think that the amount of water you would get from a passive temperature cycle system would be much compared to the ease and availability of just treating and drinking the water, and you wouldn’t likely be capturing an appreciable amount of pool water unless it was totally enclosed, as water vapor from the pool would distribute rapidly into the atmosphere – I am guessing the ambient humidity isn’t going to be much higher near the pool. You could generate water by solar still from plant matter and such just as easily as from a pool. On a side note, a still with a long enough coil will cool steam back to water, and there’s no need for wet blankets or other stuff to increase cooling. The tube will be closer to ambient at one end as it sheds heat to the air, and that will be sufficient to condense the steam back into pure water. I think your best bets in a survival situation are just to boil the water, chemically treat it, or to filter it. Pool water will remain drinkable for at least days. Running water through a tightly woven cloth and then boiling for a period of time is enough to sterilize the water, and there are not high levels of chemicals in pool water – it’s a given that you will ingest some pool water when swimming. You can do the same things with river water or well water as well. Distilling the water is just overkill. ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [April 21, 2009, 6:02am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/30 "2009-04-21T06:02:19Z")
The biggest advantage of a solar-based process is that it’s simple. I present the [Watercone](http://projecthdesign.com/wp-content/uploads/2007/11/watercone1.jpg). In a true emergency, you could jury-rig a similar device relatively easily. It may be slow (not too slow, really), but it would allow you to use your fuel for cooking food. It also works on saltwater. ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [April 21, 2009, 6:24am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/31 "2009-04-21T06:24:04Z")
> [@Alex\_Dubinsky](#): > > That sounded clever at first, but the sun’s just going to heat up the tarp way above ambient and nothing will condense on it. The water vapor will stick to the tarp and to itself and will trickle down to your edges. I’ve seen it done even in very hot places like Florida. You can use this to collect water from green vegatation as well. You don’t even need to start with water. Fill a hole with fresh green leaves and grass and cover it with plastic. Weigh down the middle with a rock and underneath put a jar to collect the drippings. It can fill a canteen in a day easily. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [April 21, 2009, 1:40pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/32 "2009-04-21T13:40:03Z")
To repeat: A little chlorine is perfectly healthy. What do you think they do at the plant that makes your tapwater? (And, again, most bottled water is just tapwater in a bottle). And chlorine goes away all by itself, so even if there’s a little too much to begin with, it will get to drinkable levels soon. The only problem comes when all the chlorine is used up. Then you start worrying about contamination. This doesn’t mean it turns instantly deadly, but starts increasing the chances of getting the runs or something. Hint: don’t crap in the pool, or wash your hands in the pool after crapping, or let animals into the pool, etc. Eventually, with just standing water, it might start getting funky with algae and what-not in there; it still might be perfectly healthy, but then again might not. So at some point, depending on how funky it is and how much fuel you have, you might want to start boiling the water. Get a good rolling boil (for a couple minutes for maximum protection), let it cool and drink. Active distillation is way, way, overkill and a huge waste of fuel. Solar distillation is fine, but not real high volume; depending on what materials you have, you might be better off spending the time looking for fuel instead of building a solar still. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [April 22, 2009, 2:54am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/33 "2009-04-22T02:54:36Z")
> [@garygnu](#): > > I present the [Watercone](http://projecthdesign.com/wp-content/uploads/2007/11/watercone1.jpg). Ok, I can see how a clear cover and a black water vessel could work. Are the pool tarps also clear? I guess this answer my other question: if solar distilling is so freakin easy, why didn’t ships use it for thousands of years. Apparently, it’s because they didn’t have transparent plastic film. ---
**Author:** ![DMC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dmc/32/18049_2.png) [@DMC](https://boards.straightdope.com/u/DMC)\ **Post date:** [April 22, 2009, 5:20am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/34 "2009-04-22T05:20:45Z")
Unless there are lots of kids and the pool is poorly maintained, your typical pool will have between 2 and 3 parts per million of total chlorine, the vast majority of which should be free available chlorine. If you have a ton of people or kids in the pool a lot, and the chemicals get neglected, you could have mostly combined chlorine, and I don’t know if I’d want to drink that. As for chlorine dissipation, most pool owners now use tabs, which contain some cyanuric acid. While this is a good thing for pool owners, it’s not so good for people who want to drink the water, as it protects the chlorine from the UV rays, somewhat, so the chlorine will stick around a bit longer. I’m not a chemist, even though as a pool owner I sometimes feel like one, but these are rough averages for some of the common attributes of a well balanced pool, so if anyone sees anything that would make it undrinkable, chime in: Chemicals, in parts per million: Chlorine: 2-3 Cyanuric acid: 40-50 Alkalinity: 120 Calcium hardness: 250 Most pools also have a ph of between 7.2 and 7.6 or so, which is definitely not a problem. A couple of things to watch for, superchlorinating (what is sometimes called “shock”, although shock comes in non-chlorine forms as well, so I don’t use that term here), which is done to free up combined chlorine. In those cases, the chlorine level can easily reach 30 ppm or even higher. Also, when a pool gets too alkaline, pool owners pour in muriatic acid. While I’m sure that dilutes pretty quickly, you certainly want to wait many hours after an application, as that is some of the nastiest stuff around. Finally, without a test kit, it’s going to be really hard to tell whether the pool is well balanced, or deadly as hell, just by looking at it. There are many ways of achieving clear, sparkling water, some of which aren’t really conducive to making it safe for drinking. There are a variety of other chemicals that are used for various purposes (sometimes simply because the pool supplier said it was needed), but the above are the basics that you can expect in most pools. I’ll let people who know about those things actually answer whether this all means that you can drink it or not. ---
**Author:** ![DMC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dmc/32/18049_2.png) [@DMC](https://boards.straightdope.com/u/DMC)\ **Post date:** [April 22, 2009, 5:28am UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/35 "2009-04-22T05:28:11Z")
I forgot to mention the salt issue mentioned above. If the pool uses a salt chlorination system (not common, but not particular rare either), the water will indeed have salt in it, but typically in the 2500 ppm range, which is probably 5-7% of the concentration found in ocean water. You can also tell if they have this system pretty easily, as it is typically inserted into the visible plumbing near the pump. ---
**Author:** ![Solfy](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@Solfy](https://boards.straightdope.com/u/Solfy)\ **Post date:** [April 22, 2009, 5:28pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/36 "2009-04-22T17:28:57Z")
> [@DMC](#): > > Also, when a pool gets too alkaline, pool owners pour in muriatic acid. While I’m sure that dilutes pretty quickly, you certainly want to wait many hours after an application, as that is some of the nastiest stuff around. Your stomach is already full of muriatic acid. It does dilute extremely rapidly. Salt water chlorinators are just generating on site the same pool chemical(sodium hypochlorite in this case) that is found in most common swimming pool chlorinators. Since the necessary sodium chloride amount in the pool is low, I don’t see a salt chlorinator being a deal breaker in terms of drinkable water. The acute oral LD50 for cyanuric acid is listed as 3400 mg/kg [Mouse]. I’m not a toxicologist, but at 40-50 ppm that doesn’t bother me. I’d suck down a glass of eau de pool if I was thirsty enough. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [April 22, 2009, 6:56pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/37 "2009-04-22T18:56:51Z")
> [@Solfy](#): > > Your stomach is already full of muriatic acid. It does dilute extremely rapidly. Your stomach is designed to contain and withstand it; the path to get it there, however, is not. Ask anyone with gastric reflux disease. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [April 22, 2009, 7:09pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/38 "2009-04-22T19:09:20Z")
> [@Q.E.D](#): > > Your stomach is designed to contain and withstand it; the path to get it there, however, is not. Ask anyone with gastric reflux disease. True enough, but how many gallons of straight muractic are added to how many gallons of pool water? Good grief, folks are acting like pool water and diluted chlorine are the devils own brew. If the apoolcalipse comes, trust me, funky pool water with icky chemicals is gonna be the least of your worries. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [April 22, 2009, 7:39pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/39 "2009-04-22T19:39:51Z")
> [@billfish678](#): > > If the apoolcalipse comes, trust me, funky pool water with icky chemicals is gonna be the least of your worries. True enough. 3/4 of the planet’s population survives on water that’s less clean/safe than your average pool. ---
**Author:** ![ivn1188](https://avatars.discourse-cdn.com/v4/letter/i/e480ec/32.png) [@ivn1188](https://boards.straightdope.com/u/ivn1188)\ **Post date:** [April 22, 2009, 7:44pm UTC](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764/40 "2009-04-22T19:44:19Z")
Not to mention pools are made for swimming in, which means you’re going to get it in your eyes, in your nose (maybe sinuses), in your mouth, in your ears, all over your skin, and you are probably going to swallow a little at some point. Admittedly pool water does kill a few people when they get it into their lungs, but I’m not sure that’s the pool chemicals at work. [Previous page](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764.md?page=1) [Next page](https://boards.straightdope.com/t/disaster-strikes-how-do-i-make-swimming-pool-water-drinkable/493764.md?page=3)